Ors to the waite



Patented Peb.25,1890.

. I Q/ -Z M i. f ,N

S. H. BARTLETT 8v H. E. WAITIL eRINDINe BLEGTRODBS Foe MIGRQPHONBS.

M j w i m, w o e (No Model.)

UNITED STATES PATENT OEEICE.

SAMUEL H. BARTLETT AND HENRY E. VAITE, OF NEW7 YORK, ASSIGN- ORS TO THE VAITE & BARTLETT MANUFACTURING COMPANY, OF SAME PLACE.

GRINDING ELECTRODES FgoR MICROPHONES.

SPECIFICATION forming part of Letters Patent'No.422,1'74, dated February 25, 1890.

Application filed June 9, 1884:. Serial No. 134,352. (No model.)

To all whom it may concern:

Be it known that we, SAMUEL H. BARTLETT and HENRY E. WAITE, citizens ofthe United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Grinding Electrodes for Microphones, of which the following is a specification.

O ur invention relates to the grinding of elecxo trodes for microphones; and it consists in subjecting a cylinder of carbon to the operations hereinafter fully set forth, so as to rapidly reduce the ends to any desired extent and without danger' of fracture.

Our inventionfurther consists of apparatus for eecting the desired operations upon the cylinder.

In the accompanying drawings, Figure l is a plan of apparatus which we employ in the zo manufacture of microphone-electrodes. Fig. 2 is a section on the line l 2, Fig. l. Fig. 3 is a longitudinal section of the holder. Fig. l is a perspective view of the carbon blank. Fig. 5 is a perspective view of the completed eleclt is usual in some classes of microphones to employ electrodes of carbon consisting of cylinders or pencils with terminal stems or iingers, as illustrated in Fig. 5. The manufacture of these electrodes each from one blank of carbon has proved to be difficult and expensive, as they must be made from cylinders or blanks of carbon of the shape of the blank X, Fig. li, and the reduction of the blank at the 3 5 ends to form the fingers a, owing to the hardness of the carbon, is difficult and apt to result in the fracture of the blank, and when such fracture ensues after a great part of the labor has been performed there is a considerable 4o loss of time and labor, and consequent expense. The fracture is most apt to result as the electrode approaches completion, when the ngers have been reduced in size, as the cutter must bear upon the thin stems with sufficient force to cut away the surface without breaking them away from the main cylinder. l'leretofore no mode of operation has been devised that would eect this result with certainty.

We have discovered that by using an emery- 5o wheel traveling at the periphery at a high speed and supplied with water to keep it moist, and by cutting the blank in the direction of its length, we are enabled to cut the carbon with rapidity without subjecting the same to such pressure as to result in fracturing the material. The use of dry wheels will not effect the purpose; but we have found that when the wheel is moistened it has a peculiar capacity and special adaptability for acting upon car- 6o bon, and will cut it with great ease and rapidity. The carbon block is presented to the edge of the wheel and revolved and moved toward the wheel until reduced to the desired extent. to be effective in these operations is shown in the drawings.

A is the frame, of suitable shape to support the bearings of the emerywheel B, and of a sliding and rotating holder or cylinder C. 7o The shaft of the wheel B is provided with a pulley c, receiving the driving-belt b, 'and the holder C fits a cylindrical socket or recess in the bearing-block E, and is provided with a handle or crank I, so that it may be both revolved and slid longitudinally in the bearing. The holder has an axial socket adapted to receive the carbon blank X, and a set-screw e serves to secure the blank in its position in the holder, in which case the axial line of 8o the blank, Fig. l, will be a distance from the face of the wheel B equal to the radius of the stem or finger oJ to be formed at the end of the blank.

After the blank has been secured in the holder the latter' is pushed longitudinally until its end is brought against the side of the wheel B, as shown in Fig. l, and the longitudinal movement is then continued and a rotary movement also imparted, so that the 9o cutting-pressure is mainly in the direction of the length of the blank, rather than radial, and there is less tendency to force the thin finger laterally from its connection with the block. Awater-reservoir J is provided with a spout 7.1;, extending over the wheel B, so as to constantly supply the wheel with water. After one finger is cut at one end of the blank An apparatus which we have found 65 the latter is reversed and the opposite end ift-e-l duced in like manner. Ve have found that by this means the blanks can be cut With certainty and dispatch and with but little liability of breaking, so that the manufacture of the electrodess rapidly and economically effected.

We do not limit ourselves to the use of the precise appliances shown and described, as it will be obvious that other means of presenting the blank to the Wheel and moving it may be employed, and that the blank may be revolved and fed laterally instead of longitudinally, although the latterI is much preferable.

We claim-- l. In the manufacture of electrodes for microphones, the method of which consists in presenting the end of a carbon cylinder to the side of a revolving Wet abrading-Wheel, with the axis of the carbon beyond the periphery of said Wheel, and revolving and feeding the blank longitudinally, substantially as de scribed.

2. In the manufacture of electrodes for microphones, the method of Which consists in revolving and feeding a cylinder of carbon longitudinally With part of its end against the side of a revolving abrading-Wheel, the axis of the cylinder being substantially parallel to the axis of 'the wheel and to one side of the periphery, substantially as and for the purpose described.

In testimony whereof We have signed our names to this specification in the presence of two subscribing Witnesses.

SAMUEL H. BARTLETT. HENRY E. WAITE. Vitnesses:

WM. H. WOODHULL, C. SPARMAN. 

